CA2097165A1

CA2097165A1 - Air conditioner

Info

Publication number: CA2097165A1
Application number: CA2097165A
Authority: CA
Inventors: Noriaki Hayashida; Hidekazu Tani; Takashi Nakamura
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1992-05-28
Filing date: 1993-05-27
Publication date: 1993-11-29
Also published as: US5347826A; JP3635665B2; DE69302225T2; DE69302225D1; EP0575063A1; ES2089728T3; JPH05322351A; EP0575063B1

Abstract

ABSTRACT OF THE DISCLOSURE
A multi-chamber heat-pump type air conditioner in which a plurality of room units (2, 3, 4) are connected to one heat source unit (1), cooling and heating can be effected selectively for each room unit (2, 3, 4), and cooling can be effected by one room unit and heating can be simultaneously effected by another, wherein the high level pressure or low-level pressure is controlled from rising high as compared to the time of normal operation, and the reliability of the compressor (17) is improved. In which, a third pressure-detector (48) is provided for detecting a rise in pressure between a compressor (17) and a four-way changeover valve (18), and a control circuit (49) is provided for controlling such that, in the event that the pressure within the pipe is below a predetermined pressure, a sixth valve (45) and a seventh valve (46) are closed, while in the event that the pressure within the pipe exceeds the predetermined pressure, the sixth valve (45) and seventh valve (46) are opened.

Description

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AIR CONDITIO~ER

BACKGROUND OF THE INVENTION
1. Field of Invention The present invention relates to control of a multi chamber heat-p~mp type air conditioner in which a plurality of room 5units are connected~to one heat source unit, and cooling and heating can be effected selecti~ely for each room unit, and cooling can be effeted by one room unit and heating can be simultaneously effected by another.

2. Descri.ption of Prior Art aA description will be given heraafter of the prior art of the present invention.
Fig. 13 is an overall schematic diagram of an air conditioner in accordance with a prior art example relating to the present invention, centering on a refrigerant system. In 15addition, Figs. 14 to 16 show states of operation during cooling and heating operation in accordance with the prior art example shown in Flg. 13, in whLch Fig. 14 is a diagram of the state of operation during only cooling or heating, while Figs.
15 and 16 show diagrams of states of the simultaneous operation ~oof cooling and heating, Fig. 15 being a diagram of a state of operation in which heating is mainly performed (a case where the capacity for heatlng operation is greater than that for cooling operation), and Fig. 16 being a diagram of a state of operation in which cooling is mainly performed (a case where 2~71~.~

the capacity for cooling operation is yreater than that for heating operation).
It should be noted that in this example a description will be given of a case where three room units are connected to one s heat source unit, but it also similarly applies to cases whe~
two or more room units are connected thereto.
In Fig. 13r reference numeral l denotes a heat source unit, and numerals 1, 2 and 4 denote room units which are connected in parallel with each other, as will be described later, and lo the same arrangement is used for the respective units. Numeral 5 denotes a relay unit which incorporates a first branching section 6, a second flow-rate controller 7, a second branching section 8, a gas-liquid separator 9, heat exchanger 10, 11, 1-2, 13, 14, a third flow-rate controller 15, and a fourth flow-rate controller 16, as will be described later.
In addition, numeral 17 denotes a compressor; 18, a four-way changeover valve for changing over the direction of circulation of a refrigerant of the heat source unit; 19, a heat source unit-side heat exchanger; and 20, an accumulator which is connecked to the compressor 17 via the four-way changeover valve 18. The heat source uni 1 is comprised of these units.
In addition, numeral 21 denotes a room unit-side heat exchanger provided for each of the three room units 2, 3, 4;
22, a large-diameter first connecting pipe for connecking together the four-way changeover valve 18 of the heat source . ~

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unit 1 and the relay unit 5 via a fourth check valve 23 which will be described later; numerals 24, 25, 2~ denote room unit-side first connecting pipes which respectively connect the room unit-side heat exchanger 21 of the room units 2, 3r 4 to the relay unit 5 and correspond to the first connecting pipe 22;
and 27 denotes a second connecting pipe having a diameter smaller than that of the aforementioned first connecting pipe and used for connecting together heat source unit-side heat exchanger 19 of the heat source unit 1 and the relay uni.t S via lo a third check valve 28 which will be described later.
In addition, numerals 29, 30, 31 respectively denote room unit-side second connecting pipes for connecting together the room unit-side heat exchanger 21 of the room units 2, 3, 4 and the relay unit S via first flow rate controllers 36, and corresponding to the sRcond connecting pipes 27.
Numeral 33 denotes a first valve for allowing the room unit-side first connecting pipes 24, 25, 26 to communicate with the first connecting pipe 22; 34 ~ a second valve for allowing the room unit-side first connecting pipes 24, 25, 26 to communicate with the second connecting pipe 27; and 35, a third valve for bypassing inlet and outlet ports of the flrst valve 33.
Numeral 36 denotes a flrst flow-rate controller which is connected in the vicinity of the room unit-side heat exchanger 21 and is controlled by a superheated amount at the outlet of the room unit-side heat exchanger 21 during cooling and by a ., 2 ~ 3 subcooled amount thereat during heating, the first flow-rate controllers 36 being connected to the room unit~side second connecting pipes 29, 30, 31.
Numeral 6 denotes the first branching section which includes the first valves 33 and the second valves 34 for selectively connecting the room unit-side first connecting pipes 24, 25, 26 to the first connecting pipe 22 or the second connecting pipe 27, as well as the third valves 35 for bypassing the inlet and outlet ports of the first valves 33.
Numeral 8 denotes the second branching section which includes the room unit-side second connecting pipes 29, 30, 31 and the second connec~ing pipe 27.
Numeral 9 denotes the gas-liquid separator disposed in -a midwa~ position of the second connecting pipe 27, and its vapor phase portion is connected to the second valves 34 at the first branchin~ sec~ion, while i~s liquid phase portion is connected to the second branching section 8.
Numeral 7 denotes the second flow-rate controller (here, an electric expansion valve) which can be opened or closed freely and is connected between the gas-liquid separator 9 and the second branching section 8.
Numeral 37 denotes a bypass pipe for connecting together second branching section 8 and the first connecting pipe 22;
15, the third flow-rate:contxoller (here, an electric expansion valve) disposed in a midway position of the bypass pipe 37; and 10, the second heat-exchange portion which is disposed 2~7~

downstream of the third 10w-rate controller 15 disposed in the midway position of the b~pass pipe 37 and effects heat exchange at a converging portion of the respective room unit-side second connecting pipes 29, 30, 31 in the second branching section 8.
s Numerals 11, 12, 13 respectively denote the third heat-exchange poxtions whlch are disposed downstream of the third flow-rate controller 15 disposed in the midway position of the bypass pipe 37, and effect heat exchange with the respective room unit-side second connecti.ng pipes 29, 30, 31 in the second lo branching section 8.
Numeral 14 denotes the first heat exchanger which is disposed downstream of the third flow-rate controller 15 of the bypass pipe 37~ and downstream of the sPcond heat-exchan~e portion 10, and effects heat exchange wLth the pipe connecting the gas-liquid separator 9 and the second flow-rate controller 7; and numeral 16 denotes the fourth flow-rate controller (here, an electric expansion valve) which can be opened or closed freely and is connected between the second branching section 8 and the first connectin~ pipe 22.
Meanwhile, numeral 28 denotes the third check valve which is disposed between the heat source unit-side heat exchanger 19 and the second connecting pipe 27, and allows clrculation of the refrigerant only from the heat source unit-side heat exchanger 19 to the second connecting pipe 27.
Numeral 23 denotes the fourth check valve which is disposed between the iour-way changeover valve 18 of the hPat source .

2~7~L~3 unit 1 and the first connecting pipe 22, and allows circulation of the refrigerant only from the first connecting pipe 22 to the four-way changeover valve 18.
Numeral 38 denotes a fifth chec~ valve which i5 disposed between the four-way changeover valve 18 of the heat source unit 1 and the second connecting pipe ~7, and allows circulation of the refrigerant only from the four-way changeover valve 18 to the second connecting pipe 27.
Numeral 39 denotes a sixth check valve which is disposed lo between the heat source unit-side heat exchanger 19 and the first connecting pipe 22, and allows circulation of the refrigerant only from the first connecting plpe 22 to the heat source unit-side heat exchanger 19.
The aforementioned third, fourth, fifth, and sixth check 1S valves 28, 23, 38, 39 constitute a channel-changeover device 4~. .
Numeral 41 denotes a first pressure-detecting means disposed between the first branching section 6 and the second flow-rate controller 7; and 42 denotes a second pressure-detecting means disposed between the second flow-rate controller 7 and the fourth flow-rate controller 16.
Next, a description will be given of the operation. First, a description will be given of the case of cooling operation only, with reference to Fig. 14. As indicated by the solid-line arrows in the drawing, a high-temperat~re high-pressure refrigerant gas discharged from the compressor 17 passes : : ,,: : ~ : : -. : , :

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through the four-way changeover valve 18, undergoes heat exchange with heat source water in the heat source unit-side heat exchanger 19, and is thereby condensed. The condensed refrigerant then passes through the ~hird check valve 28, khe s second connecting pipe 27, the gas~liquid separator 9, and the second flow-rate controller in that order, further passes through the second branching sec~ion 8 and the room unit-~ide second connecting pipes 29, 30, 31, and flows into the respective room units 2, 3, 4.
lo The refrigerant which has entered the room units 2, 3, 4 is made to undergo decompression to a low pressure by the first flow-rate controllers 36 controlled by the superheated amounts at the outlets 3f the 7'oom unit-side heat exchan~er 21. The refrigerant then undergoes hea~ exchange with the air within the rooms by means of the room uni~-side heat exchanger 21, whereupon the refrigerant evaporates and gasifies~ thereby cooling the interior of the rooms.
The refrigerant in this gaseous state forms a circulation cycle in which:it passes through the room unit-side first connecting pipes 24, 25, 26, the first valves 33, the third valves 35~ the first connecting pipe 22, the fourth check valve 23, the four-way changeover valve 18 of the heat source unit 1, and the accumulator 20, and is then sucked by the compressor 17, so as to effect the cooling operation.
At that time, the first valves 33 and the third valves 35 are open, while the second valves 34 are closed. In addition, :: ~

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since the first connecting pipe 22 is held under a low pressure and the second connecting pipe 27 un~er a high pressure at that time, the refrigerant naturally flows to the third check valve 28 and the fourth check valve 23.
S In addition, during this cycle, part of the refrigerant which has passed through the second flow-rate controller 7 enters the bypass pipe 37 and is decompressed to a low pressuxe b~ the third flow-rate controller 15. The decompressed refrigerant is then subjected to heat exchange with the room lo unit-side second connecting pipes 29, 30, 31 in the second branching section 8 by the third heat-exchange portions 11, 12, 13, and with the converging portion of the room unit-side ~econd connecting pipes 29, 30, 31 in the second branching section 8 by the second heat-exchange portion 10, and further with the refxigerant flowing into the second flow-rate controller 7 by the first heat-exchange portion 14, and is thereby evaporated. The evaporated refrigerant enters the first connecting pipe 22 and the fourth check valve 23, passes throu~h the four-way changeover valve 18 of the heat source unit 1 and the accumulator 20, and is sucked in by the compressor 17.
Meanwhile, the refrigerant at the second branching section 8, which has been cooled after being subjected to heat exchange at the first, second and third heat-exchange portions 14, 10, 2s 11, 12, 13 and provided sufficiently with subcooling, flows into the room units 2, 3, 4 to be cooled.

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Referring now to Fig. 14, a description will be siven of the case of heating operation only. Namely, as indicated by the dotted-line arrows in the drawing, the high temperature high-pressure refrigerant gas discharged from the compressor 17 passes through the four-way changeover valve 18, passes through the fifth check valve 38, the second connecting pipe 27, and the gas-liquid separator 9, passes consecutively through the second valves 34 and the room unit-side first connecting pipes 24, 25, 26, and flows into the respective room units 2, 3, 4, lo where the refrigerant undergoes hea~ exchange with the air within the rooms, and condenses and liquefies, thereby heating the interior of the rooms.
The refrigerant in this llquid~state is controlled by the subcooled amounts at the outlets of the~room unit-side heat exchanger 21, passes through the first flow-rate controllers 36 in the substantially open state, flows into the second branching section 8 from the room unit-side second connecting pipes 29, 30, 31 and converges, and further passes through the fourth flow-rate controller 16.
Here, the refrigerant is decompressed to a low-pressure gas-li~uid two-phase state by either the first flow-rate controllers 36 or ~he third and fourth flow-rate controllers lS, 16.
The refrigerant decompressed to a low pressure forms a 2S circulation cycle in which the refrigerant passes through the first connecting pipe 22, flows into the sixth check valve 39 , ~
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of the heat source unit 1 and the heat source unit-side heat exchanger 19, where the refrigerant exchanges heat with the heat source water, evaporates and assumes a yaseous state, and is sucked in by the compressor 17 through the foux-way changeover valve 18 of the heat source unit 1 and the accumulator 20, so as to effec~ the heating operation.
At that time, the second valves 34 are open, whlle the first valves 33 and the third valves 35 are closed. In addition, since the first connecting pipe 22 is held under a lo low pressure and the second connecting pipe 27 under a high pressure at that time, the refrigerant naturalIy flows to the fifth check valve 38 and the sixth check valve 39.
It should be noted that at that time ~he second flow-rate controller 7 is noxmally set in a state of being open by a predetermined minimum amount.
Referring now to Fig. 15, a description will be given of ~he case where heating is mainly carried out in the simultaneous operation of cooling and heating. As indicated by the dotted-line arrows in the drawing, the high-temperature high-pressure refrigerant gas discharged from th~ compressor 17 passes through the four-way changeovex valve 18, passes through the fifth check valve 38 and the second connecting pipe 27, is supplied to the relay unit 5, passes through the gas~ uid separator 9, passes consecutively through the second valves 34 and the room unit-side first connecting pipes 24, 25~ and flows into the respective room units 2, 3, 4 to be heated, where the -- 1~ --.~
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refrigerant undergoes heat exchange through the room unit-side heat exchanger 21, and condenses and liquefies, thereby hea~ing the interior of the rooms.
This condensed and liquefied refrigerant is controlled by the subcooled amounts at the outlets of the room unit~side heat exchanger 21, passes through the first flow-rate controllers 36, where it is slightly decompressed and flows i.nto the second branching section 8.
Part of this refrigerant passes through the room unit-side lo second connecting pipe 31, enters the room unit 4 to be cooled, enters the first flow-rate controller 36 controlled by the superheated amount at the outlet of the room unit-side heat exchanger 21. After the refrigeran~ is decomprsssed, the refrigerant enters the room unit-side heat exchanger ~1 where it undergoes heat exchange, evaporates and assumes the gaseous state to cool the interior of the room. The refrigerant then passes through the first connecting pipe 26 a~ the room unit-side, and flows into the first connecting pipe 22 via the first valve 33 and the third val~e 35. Meanwhile, a remaining portion of the refrigerant passes through the fourth flow-rate controller 16 which is controlled such that a pressure difference between the pressure detected by the first pressure-detecting means 41 and the pressure detected by the second pressure-detecting means 42 is set in a predetermined range.
2s The refrigerant then converges with the refrigerant which has passed through the room unit 4 to be cooled, passes through the - : : , .: - ,: - :. . :, . ~ , .: , 2Q9~165 large diameter first connecting pipe 22, flows into the sixth cneck valve 3g of the heat source unit 1 and the heat source unit-side heat exchanger 19, and undergoes heat exchange with the heat source water, and thereby evaporates and assumes the gaseous state.
This refrigerant forms a circulation cycle in which the room unit passes through the four-way changeover valve 18 of the heat source unit 1 and the accumulator 2a and is sucked in by the compressor 17, so as to effect the operati.on in which lo heati.ng is mainly performed.
At that time, the pressure dlf~erence between the low pressure of the room unit-side heat exchanger 36 of the room unit 4 for effecting cooling and the pressure of the heat source unit-side heat exchanger 19 becomes small since the line is changed over to the large-diameter first connecting pipe 22.
In addition, at that time, the second valves 34 connected to the room units 2, 3 are open, while the first valves 33 and the third valves 35 connected thereto are closed. The first valve 33 and the third valve 35 connected to the room unit 4 are open, while the second valve 34 connected thereto is closed.
In addition, since the first connecting pipe 22 is held under a low pressure and the second connecting pipe 27 under a high pressure at that time, the refrigerant naturally flows to the fifth check valve 38 and the sixth check ~alve 39.

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During this cycle, part of the liquid refrigerant enters the bypass pipe 37 from the converging portion of the room unik-side second connecting pipes 29, 30, 31 in the second branching section 8, and is decompressed to a low pressure by s the third flow-rate controller 15. The decompressed refrigerant is then subjected to heat exchange with the room unit-side second connecting pipes 29, 30, 31 in the second branching section 8 by the third heat exchanger 11, 12, 13, and wi~h the converging portion of the room unit-side second lo connecting pipes 29, 30, 31 in the second branching section 8 by the second heat-exchange portion 10. The evaporated refrigerant passes through the first connecting pipe 22 and the sixth check valve 39, enters the heat source unit-side heat exchanger 19 where it undergoes heat exchange with the heat source water and LS evaporated. Subsequently, the evaporated refrigerant passes through the four-way changeover valve 18 of the heat source unit 1~and the accumulator 20, and is sucked in by the compressor 17.
Meanwhile, the refrigerant at the second branching section 8, which has been cooled after being subjected to heat exchange at the second and third heat-exchange portions 10, 11, 12, 13 and provided sufficiently with subcooling, flo~s into the room unit 4 to be cooled.
It should be noted that at that time the second flow-rate 2s controller 7 is~normally set in a state of being open by a predetermined minimum amount.

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Referring now to Fig. 16, a description will be qiven of th~ case where cooling is mainly carried out in the simultaneous operation of cooling and hea~ing. As i.ndicated by the dotted-line arrows in ~he drawing, the high-temperature s high-pressure refrigerant gas discharged fro~ the compressor 17 passes through the four-way changeover valve 18, flows into the heat source unit-side heat exchanger 19 where the refrigerant undergoes heat exchange with the heat source water, and is thereby set in a gas-liquid two-phase high-temperature high-lo pressure state.
Subsequently, the refrigerant in this two-phase high-temperature high-pressure state passes through the third check valve 28 and the second connecting pipe 27, and is supplied to the gas-liquid separator 9 of the relay unit 4.
Here, the refrigerant is separated into the gaseous refrigerant and the liquid refrigerant, and the separated gaseous refrigerant passes consecutively through the second valve 34 and the room unit-side first connecting pipe 26, and flows into the room unit 5 to be heated, where the refrigerant ~o undergoes heat exchange with room air through the room unit-side heat exchanyer 21, and condenses and liquefies, thereby h~ating the interior of the room.
This condensed and liquefied refrigerant is controlled by the subcooled amount at the outlet of the room unit-side heat 2s exchanger 21, passes through the first flow-rate controller 36, 2~971 6~

where it is slightly decompressed and flo~-s into the second branching section 8.
Meanwhile, a remaining portion of the liquid ref.rigerant passes through the second flow-rate controller 7 which is controlled the pressure detected by the first pressure-detecting means 41 and the pressure detected by the second pressure-detecting means 42. The refriger2nt then converges with the refrigerant which has passed through the room unit 4 to be heated.
lo The refrigerant consecutively passes through the second branching section 8 and the room unit-side second connecting pipes 29, 30, and flows into the xespective room units 2, 3.
The refrigerant which has entered the room units 2, 3 is decompressed to a low pressur~ by the first flow-rate lS controllers 36 which is controlled by supe~heated amounts at the outlets of ~he room unit-side heat e~changer 21. The rafrigerant then flows into the room unit-s de heat exchanger 21, un~ergoes heat exchange with room air, and evaporates and gasifies, thereby cooling the interior of the rooms.
The refrigerant in this gaseous state forms a circulation cycle in which the room unit passes through the room unit-side first connecting pipes 24, 25, the first va~ves 33, the third valves 35, the first connecting pipe 22, the fourth check valye 23, the four-way changeover valve 18 of the heat source unit 1, and the accumulator 20, and is sucked in by ~he compressor 17, - , -, .. , ... : . , . .. .. . : :
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so as to effect the operation in which cooling is mainly performed.
In addition, at that time, the first valves 33 and the third valves 35 connected to the room units 2, 3 are open, while the second valves 34 connected thereto are closed. The second valve 34 connected to the room unit 4 is open, while the first valve 33 and the third valve 35 connected ~hereto are closed.
Since the first connecting pipe 22 is held under a low lo pressure and the second~ connecting pipe 27 under a high pressure at that time, the refrigerant naturally flows to the third check valve 28 and the fourth check valve 23.
During this cycle, part of the liquid refrigerant enters the bypass pipe 37 from the converging portion of the room S unit-side second connecting pipes 29, 30, 31 in the second branching section 8, :and lS decompressed to a low pressure by the third flow-rate controll~r 15. The decompressed refrigerant is then subjected to heat exchange with the room ~nit-side second connecting pipes 29, 30, 31 in the second branching section 8 by the third heat exchanger ll, 12, 13, and with the converging portion of the room unit-side second connecting pipes 29, 30, 31 in the second branching section 8 by the second heat-exchange portion lO, and further with the refrigerant flowing into the second flow-rate controller 7 by 2s the first heat-exchange portion 14. The evaporated refrigerant passes through the first connecting pipe 22 and the fourth - :. .. ~. :: ................ , check valve 23, and further passes through the four-way changeover valve 18 of the heat source unit 1 and the accumulator 20, and is sucked in by the compressor 17.
Meanwhile, the refrigerant at the second branching section 8, which has been cooled after being sùb~ected to heat exchange at the first, second and third heat-exchange portions 14r 10, llt 12, 13 and provided sufficiently with subcooling, flows into the room units~2, 3 to be cooled.
Since the conventional multi-chamber heat~pump type air lo conditioner is arranged as described above, there has been a problem in that, in the case of totally cooling operation and mainly cooling operation when the temperature of the heat source water is high, the air conditioner stops due to an abnormality in high-level pressuxe and an abnormality in discharge temperature as a result of an increase in the condensation pressure. In addition, there has been another problem in that, in the case of totally heating operation and mainly heating operation of a small-capacity room unit when the room air temperature is high, the alr conditioner similarly stops due to an abnormality in high-level pressur~ and abnormality in discharge temperature as a result of an increase in the condensation pressure. Furthermore, there has been still another problem in tha~, ln the case of totally heating operation and mainly heating operation when the heat source zs temperature is high~ ~he low-level pressure deviates from an allowable range of operation of the compressor due to a rise in :

~ ~0~71~3 evaporation pressure, thereby adversely affecting the reliability of the compressor. It should be noted that Japanese Patent Application Laid-Open (Kokai) Hei~1-118372/(1989) is known as a similar technique.
s The present invention has been devised to overcome the above-described problems, and its object is to provide a multi-chamber heat-pump type air conditioner in which a plurality of room units ars connected to one heat source unit, cooling and ~eating can be effected selectively for each room unit, and cooling can be effected by one room unit and heating can ~e simultaneously effected by another, wherein the high-level pressure or low-level pressure is controlled from rising high as compared to the time of noxmal operation, and the reliability of the compressor is not impaired.
To attain the above object; there i5 provided an air conditioner wherein a heat source unit-side heat exchànger which includes a compressor, a four-way changeover valve, a plurality of heat exchanger connected in parallel with each other and each having a fourth and a fifth valve at inlet and outlet ports thereof, and an accumulator, and a plurality of room units each including a room unit-side heat exchanger, a first flow-rate controller, and a room blower, are connected to each other via a~first connecting pipe and a second connecting pipe, a second flow-r~te controller being interposed between, 2s on the one hand, a first branching section having a first valve and a second valve for allowing one ends of the room unit-side - - - : : , , . : ; ..
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2~716~

heat exchanger of the plurality of room units to communicate selectively with the first connecting pipe or a gas-side output port of a gas-liquid separator disposed in a room unit-side pipe end of the second connecting pipe and, on the other, a s second branching section in which other ends of the plurality of room unit-side heat exchanger are connected to the second connecting pipe via the first flow-rate controllers, the second branching section and the first connecting pipe being connected to each other via a fourth 10w-rate controller, there being 0 provided a bypass pipe having one end connected to the second branching section and another end connected to the first connecting pipe via a third flow-rate controller, there being provided a heat-exchange portion for effecting heat exchange with a pipe connecting together the second connecting pipe and the first flow rate controller, a relay constltuted by ~he first branching section, the second branching section, the second flow-rate controller, the third flow-rate controller, the fourth flow-rate controller, the heat-exchange portion, and the bypass pipe lS interposed between the room unit and the plurality of room units,: characterized in that a gas side of one of the heat exchanger of the heat source unit-side heat exchanger and a discharge side of the compressor are connected to each other via a sixth valve, that a liquid side of~that heat exchanger and an inlet port of the accumulator are 2~ connected to each: other via a capillary tube and a seventh valve, and that there are provided pre~sure-detecting means for ,. . .
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detecting the pressure within a discharge-side pipe of the compressor and a control circuit for controlling such that when the pipe pressure is below a predetermined pressure, the sixth valve and the seventh valve are closed, ar.d when the pipe pressure exceeds the predetermined pressure, the sixth valve and the seventh valve are opened.
Alternatively, an arrangement may be pro~ided such that a gas side of one of the heat exchanger of the heat source unit-side heat exchanger and a d~scharge side of the compressor are lo connected to each other via a sixth valve, t~.at a liquid side of that heat exchanger and an inlet port of the accumulator are connected to each other via a capillary tu~e and a seventh valve, and that there are provided temperature-detecting means for detecting the temperature of the discharge side of the compressor and a control circuit for controlling such that when the discharge temperature is below a predetermined temperature, the sixth valve and the seventh valve are closed, and when the discharge temperature exceeds the predetermined temperature, the sixth valve and the seventh valve are opened.
Alternatively, an arrangement may be pro~ided such that a gas side of one of the heat exchanger of the heat source unit-side heat exchanger and a discharge side of t~.e compressor are connected to each other via a sixth valve, that a liquid side of that heat exchanger and an inlet port of the accumulator are connected to each other via a capillary tu~e and a seventh ~alve, and that there are provided pressure-deLecting means for -.: , : ~ , :

detecting the pressure within an inlet port-side pipe of the accumulator and a control circuit for controlling such that when the pipe pressure is below a predetermined pressure, the sixth valve and the seventh valve are closed, and when the pipe pressure exceeds the predetermined pressure, the sixth valve and the seventh valve are opened.
Alternatively, an arrangement may be provided such that a gas side of one of the~heat exchanger of the heat source unit-~ide heat exchanger and a discharge side of the compressor are connected to each other via a sixth valve, that a liquid sid~
~f that heat exchanger and an inlet port of the accumulator are connected to each other via a capillary tube and a seventh valve, that a liquid~side of that heat source unit-side heat exchanger and an~inlet port of the accumulator are connected to each other by means o an evaporation-temperature detecting circuit, and that there are provided temperature-detecting means for detecting the an evaporation temperature in the evaporation-temperature detecting means and a control circuit for contxolling such tha~t when the evaporation temperature is ~o below a predetermined temperature, the sixth valve and the saventh valve are closed, and when the evaporation temperature exceeds the predetermined temperature, the sixth valve and the seventh valve are opened.
[Operation]
The air conditioner according to the present invention is arranged as follows: The gas side o one of the heat source ` 2Q~7~

unit-side heat exchanger and the discharge side of the compressor are connected to each other via a sixth valve, the liquid side of that heat exchanger and the inlet port of the accumulator are connected to each other via a capillary tube s and a seventh valve. Pressure-detecting means for detecting the pressure within the discharge-side pipe of the compressor and a control circuit for controlling these valves are provided. When a hlgh-level pressure detected by a third pressure-detecting means is below a first set pressure, the sixth and seventh valves are closed, while when the high-level pressure rises above the first set pressure, the sixth and seventh valves are opened. Accordingly, it is possible to control an excessIve rise in the high-level pressure.
AlternativeIy, temperature-detecting means for detecting the temperature~of the discharge side of the compressor and a control circuit for controlling these valYes are provided.
When the discharge temperature detected by the temperature-detecting means is below a first predetermined temperature, the sixth and the seventh vaIves are closed, while when the discharge temperature rises above the first set temperature, the sixth and seventh valves are opened. Accordingly, it is possible to con~rol an excess rise in the discharge temperature.
Alternatively, pressure-detecting means for detecting the pressure within an inlet port-side pipe of the accumulator and a control circuit for controlling these valves are provided.

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When the low-level pressure detected by a fo~rth pressure-detècting means is below a second set pressure, the sixth and seventh valves are closed, while when it rises abo~e the second set pressure, the sixth and seventh valves are opened.
Accordingly, it is possible to control an excessive rise in the low-level pressure.
Alternatively, the liquid side of the heat source unit-side heat exchanger and an inlet port of the accumulator are connected to each other by means of an evaporation-temperature detacting circuit, and a control circuit for controlling these Yalves i9 provided. When the evaporation temperature detected by the evaporation-temperature detecting means i5 below a second predetermined temperature, the sixth and seventh valves are closed, while when the evaporation temperature rises above the second set temperature, the sixth and seventh valves are opened. Accordingly, ~it is possible to control an excessive rise in the e~aporation temperature.

BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is an overall schematic diagram of an air conditioner in accordance with a first embodiment of the invention, centering on a refrigerant system;
Fig. 2 is a circuit diagram of the refrigerant illustrating the state of operation of only cooling or heatin~ by the air conditioner in accordance with the first embodiment of the present invention;

~ ~f ~ ' ~

2Q971~

Fig. 3 is a circuit diagram of the refrigerant illustrating the state of operation of mainly heating by the air conditioner in accordance with the first embodiment of the present invention;
s Fig. 4 is a circuit diagram of the refrigerant illustrating the state of operation of mainly cool.ing by the air conditioner in accordance with the first embodiment of the present invention;
Fig. 5 is a block diagram illustrating a coniguration of lo a control system of a first controller of the alr conditioner in accordance with the first embodiment of the present invention;
FLg . 6 is a f lowchart of the control system of -the first controller of the air conditioner in accordance with the first embodiment of the present invention;
Fig. 7 is a block diagram illustrating a configuration of a control system of a second controller of the air conditioner in accordance with a second embodiment o the present invention;
~o ~ Fig. 8 is a flowchart of the control system of the second controller of the air conditioner in accordance with the second embodiment of the present invention;
Fig. 9 is a block diagram illustrating a configuration of a control system of a third controller of the air conditioner 2s in accordance with a third embodiment of the present invention;

.

2~97~L6~

Fig. lO is a flowchart of the control system of the ~hird controller of the air conditioner in accordance with the third embodiment of the present invention;
Fig. 11 is a block diagram illustrating a configuration of s a control system of a fourth controller of the air conditioner in accordance with a fourth embodiment of the present invention;
Fig. 12 is a flowchart of the control system of the fourth controller of the alr condltioner in accordance with the fourth embodiment of the present invention;
Fig. 13 is an overall schematic diagram of an air conditioner in accordance with a prlor art example relating to the invention~ centering on the xefrigerant system;
Fig. 14 is a circuit diagram of the refrigerant illustrating the state of;operation of onl~ cooling or heating by the air condi~tioner ln accordance with the prlor art example relating to the present invention;
Fig. 15 is a circuit diagram of the refrigerant illustrating the state of operation of mainly heating by the air conditioner~ in~ accordance~ wlth the prior art example relating to the present invention; and Fig. 16 i~s a circuit diagram of the refrigerant illustrating the state of operation of mainly cooling by the air conditioner in accordance with the prior art example ~s relating to the present invention.

2~7~6~

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment Hereafter, a description will be given of an embodiment of the present invention.
s Fig. 1 is an overall schematic diagram of an air conditioner in accordance with an embodiment of the present invenkion, centering on a refrigerant system. Figs. 2 to 4 are diagrams illustrating states of operation during cooling and heating operation in the first embodiment, in which Fig. 2 is a diagram of a state of operation of only cooling or heating, Fig. 3 is a diagram of a state of operation in which heating is mainly performed (a case where the capacity for heating operation is greater than that for cooling operation) in the simultaneous operatîon of cooling and heating, and Fig. 4 is a diagram of a state of operation in which cooling is mainly performed (a case where the capacity for cooling operation is greater than that for heating operation) in the simultaneous operation of cooling and heating.
It should be noted that in this first embodiment a description will be glven of a case where three room units are connected to one heat source unit, but it also similarly applies to cases where two or more room units are connected thereto.
In Fig. 1, reference numeral l denotes a heat source unit, and numerals 1, 2 and 4 denote room units which are connected in parallel with each other, as will be described later, and 20~7~

the same arrangement is used for the respective units. Numeral 5 denotes a relay unit which incorporates a first branching section 6, a second flow-rate controller 7, a second branching section 8, a gas-liquid separator 9, heat exchange-portions lO, 11, 12, 13, 14, a third flow-rate controller 15, and a fourth flow-rate controllex 16, as will be described later.
In addition, numeral 17 denotes a compressor, -18, a four-way changeover valve for changing over the direction of circulation of a refrigerant of the heat source unit; 19~ a lo heat source unit-side heat exchanger consisting a plurality of heat exchanger which are connected in parallel with each other and each having a fourth valve 43 and a fifth valve 44 at inlet and outlet ports thereof; and 20, an accumulator which is connected to the compressor 17 vla the four~way changeover valve 18. Numeral 45 denotes a sixth valve connected to a bypass pipe for connecting the gas side of one of the aforementioned heat source unit-side heat exchanger l9 and the discharge side of the compressor 17. Numeral 46 denotes a seventh valve connected to a bypass pipe for connecting the liquid side of; that heat exchanger and an inlet of the accumulator 20 via a capillary tube 47. Numeral 48 denotes a third pressure-detecti:ng means disposed between the compressor 17 and the four-way changeover valve 18.
In addition, numeral 21 denotes a room unit-side heat exchanger provided for each of the three room units 2, 3, 4;
22, a large-diameter first connecting pipe for connecting 2 ~ 9 ~

together the four-way changeover valve 18 of the heat source unit 1 and the relay unit S via a fourth check valve 23 which will be described later; numerals 24, 25, 26 denote room unit-side irst connecting pipes which respectively connect the room unit-side heat exchanger 21 of the room units 2, 3, 4 to the relay unit 5 and correspond to the first connecting pipe 22;
and 27 denotes a second connectlng pipe having a diameter smaller than that o the aforementioned first connecting pipe and used or connectinq together heat source unit-side heat lo exchanger 19 of the heat source unit 1 and the relay unit 5 via a third check valve 28 whlch will be described later.
In addition, numerals 29, 30, 31 respectively denote room unit-side second connectlng pipes for connecting together the : room unit-side heat exchanger 21 of the room units 2, 3, 4 and lS the relay unit S, and corresponding to the second connecting pip~s 27.
Numeral 33 denotes a first valve or allowing the room : unit-side first connecting pipes 24, 25, 26 to communicate with the irst connecting pipe 22; 34, a second valve or allowing the room unit-side first connecting pipes 24, 25, 26 to communicate wi.th the second connecting pipe 27; and 35, a third valve or bypassing inlet and outlet ports of the first valve 21.
Numeral 36 denotes~a first flow-rate controller which is connected in the vicinity of the room unit-side heat exchanger 21 and is controlled by a superheated amount at the outlet of .

2~7~6~

the room unit-side heat exchanger 21 during cooling and by a subcooled amount thereat during heating, the first flow-rate controllers 36 being connected to the room unit-side second connecting pipes 29, 30, 31.
Numeral 6 denotes the first branching section which includes the first valves 33 and the second valves 34 for selectively connecting the room unit-side first connecting pipes 24, 25, 26 to the first connecting pipe 22 or the second connecting pipe 27, as well as the third valves 35 for bypassing the inlet and outlet ports of the first valves 33.
Numeral 8 denotes the second branchlng section which includes the room unit-side second connecting pipes 29, 30, 31 and the second connecting~pipe 27~ -Numsral 9 denotes the:gas-liquid separator disposed in a ~midway position of the second connectlng plpe 27, and its vapor phase portion is connected to the second valves 34 a-t the first branching section, while its liquid phase portion is connected to the second branching section 8.
Numeral 7 denotes the second flow-rate controller (here, an electric expansion valve) which can be opened or closed freel~ :
and is connected between the gas-liquid separator 9 and the second branching sectlon 8.
Numeral 37 denotes a bypass pipe for connecting together second branching section 8 and the first connecting pipe 22;
15, the third flow-rate controller (here, an electric expansion valve) disposed in a midway position of the bypass pipe 37; and : - 29 --10, the second heat-exchange portion which is disposed dowmstream of the third flow-rate controller 15 disposed in the midway position of the bypass pipe 37 and effects heat exchange at a converging portion of the respective room unit-side second connecting pipes 29, 30, 31 in the second branching section 8.
Numerals 11, 12, 13 respectively denote the third heat-exchange portions which are disposed downstream of the third flow-rate controller 15 disposed in the midway position of the bypass pipe 37, and effect heat exchange w}th the respective lo room unit-side ~econd connecting pipes 29, 30, 31 in the second branching section 8.
Numeral 14 denotes the first heat exchanger which is disposed downstream of the third flow-rate controller 15 of the bypass pipe 37 and downstream of the second heat-exchange portion 10, and:effects heat exchange with the pipe connecting the gas-liquid separator 9 and the second flow-rate controller 7; and numeral 16 denotes the fourth flow-rate controller (here, an electric expansion valve) which can be opened or closed freely and is connected between the second branching section 8 and the first connecting pipe 22.
.

Meanwhile, numeral 32 denotes the third check valve which is disposed between the heat source unit-side heat exchanger 19 and the second connecting pipe 27, and allows circulation of the refrigerant only from the heat source unit-side heat exchanger 19 to the second connecting pipe 27.

2 Q ~

Numeral 23 denotes the fourth check valve which is disposed between the four-way changeover valve 18 of the heat source unit l and the first connecting pipe 22, and allows circulation of the refrigerant only from the first connecting pipe 22 to the four-way changeover valve 18.
Numeral 38 denotes a fifth check valve which is disposed between the four-way changeover valve 18 of the heat source unit l and the second connecting pipe 27, and allows circulation of the refrigerant only from the four-way lo changeover valve 18 to the second connecting pipe 27.

.
Numeral 39 denotes a sixth check valve which is disposed between the heat source unit-side heat exchanger 19 and the first connecting pipe 22, and allows clrculation of the refrigerant only from the first connecting pipe 22 to the heat source unit-side heat exchanger 19.
The aforementioned~thirdr fourth, fifth, and sixth check valves 28,, ~3, 38, 39 constitute a channel-changeover device 40.
Numeral 41 denotes a first pressure-detecting means disposed between the first branching section 6 and the second flow-rate controller 7; and 42 denotes a second pressure-detecting means disposed between the second flow-rate controlier 7 and the fourth flow-rate controller 16.
Numeral 45 denotes the sixth valve connected to a pipe for connecting the compressor 17 and the heat source unit-side heat exchanger 19, and numeral 46 denotes -the seventh valve provided in the pipe for connecting the accumulator 20 and the heat source unit-side heat exchanger 19, together with a capillary tube 47.
Next, a description will be given of the operation. First, a description will be given of the case of cooling operatio~
only, with reference to Fig. 2. As indicated by the solid-line arrows in the drawing, a high-temperature high-pressure refrlgerant gas discharged from the compressor 17 passes through the four-way changeo~er valve 18, undergoes heat lo exchange with heat source water in the heat source unit-side heat exchanger ].9, and is thereby condensed. The condensed refrigerant then passes through the third check valve 28, the second connecting pipe 27, the gas-liquid separator 9, and the second flow-rate controller~ in that order, further passes through the second branching section 8 and the room unit-side second connecting plpes 29, 30, 31, and flows- into the : respective room units 2, 3, 4.
The re~rigerant which has entered the room units 2, 3, 4 is made to undergo decompression to:a low pressure by the first flow-rate control~lers:36 controlled by the superheated amounts at the outlets of the room unit-side heat exchanger 21. The refrigerant then undergoes heat~exchange with the air within th rooms by means of ~he room unit-side heat exchanger 21, whereupon the refrigerant evaporates and gasifies, thereby cooling the int rior of the rooms.

: - 32 -.

2~97~

The refrigerant in this gaseous state forms a cixculation cycle in which it passes through the room unit-side first connecting pipes ~4, 25, 26, the first valves 33, the third valves 35, the first connecting pipe 22, the fourth check valve 23, the four-way changeover valve 18 of the heat source unit 1, and the accumulator 20, and is then sucked by the compressor 17, so as to effect the cooling operation.
~t that time, the firsk valves 33 and the third valves 35 are open, while the second valves 34 are closed. In addition, lo since the first connecting pipe 22 is held under a low pressure and the second connecting pipe 27 under a high pressure at that time, the refrigerant naturally flows to the third check valve 28 and the fourth check valve 23.
In addition, during this cycle, part of the refrigerant lS which has passed through the second flow-rate controller 7 enters the bypass pipe 37 and is decompressed to a low pressure by the third flow-rate controller 15. The decompressed refrigerant is then subjected to heat exchange with the room unit-side second connecting pipes 29, 30, 31 in the second branching section )3 b~ the third heat-exchange portions 11, 12, 13, and with the convergi.ng portion of the room unit-side second connecting pipes 29, 30, 31 in the second branching section 8 by the second heat-exchange portion 10, and further with the refrigerant flowing into the second flow rate controller 7 by the first heat-exchange portion 14, and is thereby evaporated. The evaporated refrigerant enters the 7 ~

first connecting pipe 22 and the fourth check valve 23 r passes through the four-way changeover valve 18 of the heat source unit 1 and the accumulator 20, and is sucked ln by the compressor 17.
Meanwhile, the refrigerant at the second brallching section 8r which has been cooled after being subjected to heat exchange at the first, second and third heat-exchange porti-ons 14, 10, 11, 12, 13 and provided sufficiently with subcooling, flows into the room units 2, 3, 4 to be cooled.
Referring now to Fig. 2, a description will be given of the case of heating operation only. Namely, as indicated by the dotted-line arrows in the drawing, the high-temperature high-pressure refrigerant gas dlscharged from the compressor 17 passes through the four-way changeover valve 18, passes through 15~ the fifth check valve 6, the second connecting pipe 27, and the gas-liquid separator 9, passes consecutively through the second valves 34 and the room unit-side first connecting pipes 24, 25, 26, and flows into the respective room units 2, 3, 4, where the refrigerant undergoes heat exchange with the air within the rooms, and condenses and liquefies, thereby heating the interior of the rooms.
The refrigerant i.n this liquld state is controlled by the subcooled amounts at the outlets of the room unit-side heat exchanger 21, passes through the first flow-rate controllers 36 ~5 in the substantially open state, flows into ths second branching section 8 from the room unit-side second connecting ~7~

pipes 29, 30, 31 and converges, and ~urther passes through the fourth flow-rate controller 16.
Here, the refrigerant is decompressed to a low-pressure gas-liquid two-phase state by either the first flow~rate controllers 36 or the third and fourth flow-rate cantrollers 15, 16.
The refrigerant decompressed to a low pressure forms a circulation cycle in which the refrigerant passes through the first connecting pipe 22, flows into the sixth check valve 39 of the heat source unit 1 and the heat source unit-side heat exchanger 19, where the refrigerant e~changes heat with the heat source water, evaporates and assumes a gaseous state, and is sucked in by the compressor 17 through the four-way changeover valve 18 of the heat source unit 1 and the accumulator 20, so as to effect the heating operation.
At that time, the second valves 34 are open, while the first valves 33 and the third valves 35 are closed. In addition, since the flrst connecting pipe 22 is held under a low pressure and the second connectLng pipe 27 under a high pressure at that time, the refrigerant naturally flows to the fifth check valve 38 and the sLxth check valve 39.
It should be noted that at that time the second flow-rate controller 7 is normally set in a state of being open by a predetermined minimum amount.
Referring now to Fig. 3, a description will be given o~ the case where heating is mainly carried out in the simu]taneous ~; ~ .. . . :., - ,...... . .. , i . ~ . . -.~ :

L 6 ~

operation of cooling and heating. As indicated by the dotted-line arrows in the drawing, the high-temperature high-pressure refrigerant gas discharged from the compressor 17 passes through the four-way changeover valve 18, passes through the S fifth check valve 38 and the second connecting pipe 27, is supplied to the relay unit 5, passes through the gas-liquid separator 9, passes consecutively through the second valves 34 and the room unit-side first connecting pipes 24, 25, and flows into the respective room units 2, 3, to be heated, where the lo refrigerant undergoes heat exchange through th room unit-side heat exchanger 21, and condenses and liquefies, thereby heating the interior of the rooms.
This condensed and liquefied refrigerant is controlled by the subcooled amounts at the outlets of the room unit~side heat exchanger 21, passes through the first flow-rate controllers 36, where it is slightly~decompressed and flows into the second branching section 8.~ ~ ~
Part of this~refrigerant passes through the room unit-side second connecting pipe 31, enters the room unit 4 to be cooled, enters the first flow-rate controller 36 controlled by the superheated amount at the outlet of the room unit-side heat exchanger 21. After the refrigerant is decompressed, the refrigerant enters the room unit~side heat exchanger 21 where it undergoes heat exchange, evaporates and assumes the gaseous state to cool the interior of the room. The refrigerant then passes through the xoom unit-side first connecting pipe 26, and :- , . , , ... . . : : ' ,'. . ! ' '. . , - .' " ' ' ' ' " ' '. : `- ''' ' ' .
: . . ' ' ' ': : : ' ' ' ~ ' :
::: : ' ,-, . ': :-: .. : ' . , : `: : : .,:

2~9716~ ~

flows into the first connecting pipe 22 via the first valve 33 and the third valve 35.
Meanwhile, a remaining portion of the refrigerant passes through the fourth flow-rate controller 16 which is controlled s such that a pressure difference between the pressure detected by the first pressure-detecting means 41 and the pressure detected by the second pressure-detecting means 42 is set in a predetermined range. The refrigerant then converges with the refrigerant which has passed through the room unit 4 to be lo cooled, passes through the large~diameter first connecting pipe 22, flows into the slxth check valve 39 of the heat source unit 1 and the heat source unit-side heat exchanger 19, and undergoes heat exchange with the heat source water, and thereby evaporates and assumes the gaseous state.
This refrigerant forms a circulation cycle in which the room~unit passes through the four-way;changeover valve 18 of the heat source unlt~l and the accumolator 20 and is sucked in by the compressor 17, so as to effect the operation in which :
heating is mainly performed.
At that time, the pressure difference between the low pressure of the~room unit-side heat exchanger 21 of the room unit 4 for effectlng ~cooling and the pressure of the heat source unit-side heat exchanger 19 becomes small since the line is changied over to the large-diameter first connecting pipe 22.
In addition, at that time, the second valves 34 connected to the room units 2,~ 3 are open, while the first valves 33 and the third valves 35 connected thereto are closed. The first valve 33 and the third valve 35 connected to the room unit 4 are open, while the second valve 34 connected thereto is closed.
In addition, since the first connecting pipe 22 is held under a low pressure and the second connecting pipe 27 under a high pressure at~that time,:the refrigerant naturally flows to the fifth check vaIve 38 and:the sixth check valve 39.
During this cycle, part~of the liquid refrigerant enters lo the~ bypass pipe: 37 from the converging portion of the room : unit-s.ide second connect~ng p1pes 29j 30, 31 in the second branching section 8, and is;decompressed to a low pressure by the third flow-rate controller 15. The decompressed xefrigerant is then subjected to heat exchange with the room I5 ~an~it-side second~connecting p1pes 29, 30, 31 in the second branching sect1on 8:by~the th1rd:heat exchanger 11, 12, 13, and with~ the converging port~on o~f the room unit-side second conneoting pipes~ 29, 30, 31 in the second branching section 8 by the second heat-exchange ~portion 10. The evaporated refrigerant passes through the first connecting pipe 22 and the sixth check valve :39,~enters the heat source unit-side heat exchanger 19 where it undergoes heat exchange with heat source water and is evaporated. Subsequently, the evaporated refrigerant passes through the four-way changeover valve 18 of ~2s the heat source unit 1 and the accumulator 20, and is sucked in by the compressor 17.

.. .. . ., .. . ,~ . . . - . .
, ,;. . ..

2~7~

Meanwhile, the refrigerant at the second branching section 8, which has been cooled after being subjected to heat exchange at the second and third heat-exchange portions 10, 11, 12, 13 and provided sufficiently with subcooling, flows into the room unit 4 to be cooled.
It should be noted that at that time the second flow-rate controller 7 is normally set in a state of being open by a predetermined minimum amount.
Referring now to Flg. 4, a description will be given of the case where cooling is mainly carried out in the simultaneous operation of coollng and heating.
As indicated by the solid-llne arrows in the drawing, the high-temperature high-pressure refrigerant gas discharged from the compressor 17 passes through the four-way changeover valve 18; flows into the heat source unit-side heat exchanger l9 .
where the refrigerant undergoès heat exchange with the heat :
source water, and is thereby set in a gas-liquid two-phase high-temperature hlgh-pressure state.
Subsequently, the refrigerant in this two-phase high-temperature high-pressure state passes through the third check valve 28 and the second connecting pipe 27, and lS supplied to the gas-liquid separator 9 of the relay unit 5.
Here, the refrigerant is separated into the gaseous refrigerant and the liquid refrigerant, and the separated gaseous refrigerant passes consecutively through the second valve 34 and the room unit-side first connecting pipe 26, and :. .. .. .

. - ~ ,, ~ ::, -, . :. .

2 0 9 7 3L ~ 3 flows into the room unit 4 to be heated, where the refrigerant undergoes heat exchange with room air thxough the room unit-side heat exchanger 21, and condenses and liquefies, thereby heating the interior of the room.
This condensed and liquefied refrigexant is contxolled by the subcooled amount at the outlet o the room unit~side heat exchanger 21, passes through the first ~low-rate controller 36, where it is slightly decompressed and flows into the second branching section 8.
~lo ~ Meanwhile, a ~remaining porti~on of the liqui.d refrigerant ~passes through the second~ flow-rate~controller 7 which is controlled~the pressure ~detected~by~ the first pressure-detecting means 41 and the pressure~ detected by the second pressure~-detecting~means 42 ~ The;~refrigerant then converges~
S ~ with;the ref~rigerant~`which~has~passed~through~the room unit to be~heated.
The~ refrlgerant~ con~secutively~passes through the second branchlng section 8~and ~the~ room~unit-side second conneCtiDg pipes 29, 30~, and flows into the~ resp`ective room units 2, 3.
20 ~The~refrigerant whi~h has; entered the room units 2, 3 is decompressed~ to~ a~ low ~pressure~by the~ first flow-rate c`ontrollers 36 which is contro~led~by superheated amounts~at the outlets of the room unit-side heat exchanger 21. The ~refrLgerant then flows lnto;the room unit-side heat exchanger 21, undergoes heat exchange~with~room air, and e~aporates and ~; gasifies, thereby coollDg the interior o~f the;rooms.

: ` . . . ' ' ' t"' '`' '` "' ' ' ' ;` ." ' ` '~ "''~ ' `'"' ' ' 2~9716~

The refrigerant in this gaseous state forms a circulation cycle in which the room unit passes through the room unit-side first connecting pipes 24, 25, the first valves 33, the third valves 35, the first connecting pipe 22, the fourth check valve 23, the four-way changeover valve 18 of the heat source unit l, and the accumulator 20, and is sucked in by the compressor 17, so as to effect the operation in which cooling is mainly performed.
In addition, at that time, the first valves 33 and the lo third valves 35 connected to the room units 2, 3 are open, while the second valves 34 connected thereto are closed. The second valve 34 connected to the room unit 4 is open, while the first valve 33 and the third valve 35 connected thereto are closed.
Since the first~connect.ing pipe 22 is held under a low pressure and the second~ connecting plpe 27 under a high :
pressure at that time, the ref~rigerant naturally flows to the ; ~ thlrd check valve 28 and the fourth check valve 23.
: .
~ During this cycle, part of the liquid refrigerant enters the bypass plpe 37 from the converging portion o~ the room unit-side second connecting pipes 29, 30, 31 in the second branching section 8, and is decompressed to a low pressure by the third flow~rate~ controller 15. ~ The decompressed refrigerant is khen subjected~to heat exchange wlth the room unit-side second connecting pipes 29, 30, 31 in the second branching section 8 by the third heat exchanger 11, 12, 13, and _ 41 -,; , , - ,. ~ ::
.: .: ::: : :: : .. . ~ :

20971~

with the converging portion of the room unit-side second connecting pipes 29, 30, 31 in the second branching section 8 by the second heat-exchange portion 10, and further with the refrigerant flowing into the second flow-rate conkroller 7 by the first heat-exchange portion 14. The evaporated refrigerant passes through the first connecting pipe 22 and the fourth check valve 23, and further passes through the four-way changeover valve 18 of the heat source unit l and the accumulator 20, and is sucked in by the compressor 17.
lo Meanwhile, the refrigerant at the second branching section a, which has been cooled after belng subjected to heat exchange at the first, second and third heat-exchange portions 14, lO, 11, 12, 13 and provided sufficiently with subcooling, flows into the room units 2, 3 to be cooled.
Next, a descriptlon wlll be given of the control of the fourth~valve 43, the~flfth valve~44, the sixth valve 45, and - the~seventh valve~46 ~when~ the~high-level pressure has risen abave a f;irs~ set pressure.~
Fig. 5 shows a mechanism for controlling the fourth valve 43, the fifth valve 44, the sixth valve 45, and the seventh valve 46, and reference numeral 49 denotes a flrst control circuit for controlling the fourth to seventh valves by means of the pressure detected by the third pressure-detecting means 48.
Fig. 6 is a flowchart illustrating the detalls of~control effected by the first control circuit 49.
~:

2Q~7~

In the air conditioner in accordance with this first embodiment, the high-level pressure becomes high in the case of totally cooling operation and mainly cooling operation when the heat-source water temperature is high. In addition, the high-level pressure becomes high also in the case of totally heatingoperation and mainly heating operation using a small-capacity room unit when the room air temperature is high. Accordingly, control is effected such that the sixth valve 45 and the seventh valve 46 are opened when the third pressure-detecting lo means 48 has detected that the~high-level pressure is more than the first~set pressure. Through the above-descri.bed control, the high-pressure liquid refrigerant condensed by the heat exchanger is bypassed to be set to a lower pressure via the capillary tube, so~that the high-level pressure and the low-leveI pressure become lowi thereby preven-ting the air condltloner frorn stopplng due to~ an abnormality in the hlgh-level~pressure.
Next, a descriptlon will~be given of the details of control effected by the first control circuit 49 in this first zo embodiment wlth reference to the ~lowchart shown in Fig. 6.
When the air conditioner performs totally cooling operation and mainly cooling operation,~ in Step S91, a comparison is made between a high-level ~pressure ;;Pd detected by the third pressure-detecting means 48 and a first set pressure P1. Here, if a deterrnination is made that the high-level pressure Pd is greater than the set pressure P1, the operation proceeds to : :: . : . ; -.

2 ~

5tep S92 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed.
If it is determined in Step S92 that the sixth valve 45 and the seventh valve are closed, the operation proceeds to Step S93 to open the sixth valve 45 and the seventh valve. If it is determined in Step S92 that the sixth valve 45 and the seventh valve 4& are open, ~he operation returns to Step S91.
If it is determined in Step S91 that the high-level pressure Pd is not more than the first set pressure P1, the lo operation proceeds:to Step S94 to determine whether the sixth valve 45 and the seventh valve are open or closed. If it is determined in Step S94 that the sixth valve 45 and the seventh valve 46 are open, the:operation proceeds to Step S95 to close the sixth valve 45 and the seventh valve 46.
If it is determined:in~Step S94 that the sixth valve 45 and : the seventh valve 46 are;closed, the operation returns to Step S ~
~;: When the air:conditioner performs totally heating operation and mainly cooling operation, in Step S96, a comparison is made between the high-level pressure Pd detected by the third pressure-detecting means 48 and the first set pressure Pl.
Here, if a determination:is made that the high-level pressure Pd is greater than the set pressure P1, the operation proceeds to Step S97 to determine whether the fourth valve 43 and the 5 fifth valve 44 are open or closed.
:

- - ~. ~ ,:, i ~ ,.. . .. . .

If it is determined in Step S97 that the fourth valve 43 and the fifth valve 44 are closed, the opera~ion proceeds to Step S98 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed. If it is determined in s Step S98 that the sixth valve 45 and the seventh valve 46 are closed, the operation proceeds to Step S99 to open the sixth and seventh valves. If i-t is determined in Step S99 that the sixth valve 45 and the seventh valve 46 are open, the operation returns to Step S96.
lo If it is determined in Step S97 that the fourth valve 43 and the fifth valve 44 are open, the fourth valve 43 and the fifth valve 44 are closed in Step S100, and the operation proceeds to Step S101. In Step SlO1, a determination is made as to whether the sixth valve 45 and the seventh valve 46 are open or closed. If a determination is made that they are open, the operation proceeds to~Step S102 to open the sixth valve 45 and the seventh~valve 46~, and the operation returns to Step S96. If it is determined in Step S101 that the sixth valve 45 and the seventh valve 46 are open, the operation returns to Step S96.
If it is determined in Step S96 that the high-level pressure Pd is not more than the first set pressure P1, the operation proceeds to Step S103 to determine whether the sixth valve 45 and the seventh valve 46 are open ox closed. If it is determined in Step 5103 that the sixth valve 45 and the seventh valve 46 are open, the operation proceeds to Step S104 to open - ~5 -.... ..... ...
: ~ - ~; :~ :::: ;:. - , , . .:
, . ., - : ,~

the sixth valve 45 and the seventh valve 46, and the operation returns to Step 596. If it is determined in Step S104 that the sixth valve 45 and the seventh valve 46 are closed, the operation returns to Step S96.

s Second Embodiment ~ext, a description will be given of the control of the ~ : .
fouxth valve 43, the fifth valve 44, the sixth valve 45; and the seven~h valve 46 when;the discharge temperature has risen above a first set temperature.~

:: :~ :
~; loFig. 7 shows a mechanism~for controlling the fourth valve 43 r the fifth valve 44, the ~sixth valve 45, and the seventh valve 46, and reference numeral~50 denotes a second control ;circult for controlling the f~ourth;~to seventh valves by mean~s~
of the pressure detected~by a~;f~irst prèssure-detecting means Fiq.~8 lS a:flowchart~;~Lllu;strating the details of controI
effected~by the second control circuit~S0.
In the~ air conditioner in accordance with this second embodiment, in the case of totally cooling operation and mainly ~cooling~operation~when the~ heat-source water temperature is hLgh, the~;discharge~tempera~ture~becomes high as;the hlgh-level pressure becomes high. In additlon, in ~he case of totally heating operation and~mainly heating operation using a small-capacity~room unit~when the room air temperature is high, the ~2s;~ dlscharge temperature~ also becomes high as the ~high-level ~ :~

: ~ :

:

-: : -: : ~ , : , ,: ~ :, ,;- -- . .. ,1''.,.. , .. . ., ~ .,. . ., - ,: - .. , : .

: : . : ; . :: .: : . - : : . ~ : :

2~9~16~

pressure becomes high. Accordingly, control is effected such that the sixth valve 45 and the seventh valve 46 are opened when the first temperature-detecting means 50 has detected that the discharge temperature is more than the first set s temperature. Through the above-described control, the high-pressure liquid refrigerant condensed by the heat exchanger is bypassed to be set to a lower p.ressure via the capillary tube, so that the high-level pressure and the low-level pressure become low, thereby making it possible to control a rise in the lo discharge temperature.
Next, a description will be given of the details of control effected by the second control circuit 50 in this second embodiment with reference to the flowchart shown in Fig. 8.
: When the air conditioner performs totally cooling operation and mainly cooling operation, in:Step S106, a compa.rison is made between a discharge temperature Td~detected by the first temperature-detecting means 51 and a first set temperature Tl.
:
Here, if a determination is made that the discharge temperature Td is greater than the set temperature Tl, the operation proceeds to Step S107 to determine whether the sixth valve 45 and the seventh valve 46~are ~pen or closed.
:: If it is determLned ln:Step S107 that the sixth valve 45 and the seventh valve 46 are closed, the operation proceeds to Step S108 to open the sixth valve 45:and the seventh valve 46.
If it is determined in Step S107 that the sixth valve 45 and :

::

, :: : . . : - -, : .,, .,: . .. . .

2~9~

the seventh valve 46 are open, the operation returns to Step S106.
If it is determined in Step S106 that the discharge temperature Td is not more than the first set temperature T1, the operation proceeds to Step SlO9 to determine whether the sixth valve and the seventh valve 46 are open or closed. If it is determined in Step S109 that the sixth valve 45 and the seventh valve 46 are open, the operation proceeds to Step S110 to close the sixth valve 45 and the seventh valve 46.
lo If it is determined in Step S109 that the sixth valve and the seventh valve 46~are closed, the operation returns to Step Sl06.
.
When the air conditioner performs totally heating operation and mainly cooling operation,:in Step S~111, a comparison is made between the~di;schar~e~temperature Td:detscted by the firs-t temperature-detecting~means 51 and the first sét temperature T1. Here, if ~a :determlnation ls made that the discharge temperature Td is greater than the set temperature T1, the ~ operatlon proceeds to Step S112 to determine whether the fourth zo valve 43 and the fifth valve 44 are open or closed.
~ If it is determined in Step S112 that the fourth valve 43 and the fifth valve~:44 are closed, the operation proceeds to Step S113 to determine whether the sixth valve 45 and the seventh valve 46 are closed. If it is determined in Step 5113 that the sixth valve 45 and the seventh valve 46 are closed, the operation proceeds to Step S114 to open the sixth valve 45 :, . , :::, ,:. . :: ~:

~7~

and the seventh valve 46. If it is determined in Step S113 that the sixth valve 45 and the seventh valve 46 are open, the operation returns to Step S111.
If it is determined in Step S112 that the fourth valve 43 s and the fifth valve 44 are open, the fourth valve 43 and the fifth valve 44 are closed in Step S115, and the operation proceeds to Step S116 In Step S116, a determinatlon i.s made as to whether the sixth valve 45 and the~seventh valve 46 are open or closed. I~ a determination is made that they are lo closed, the operation proceeds to Step S117 to open the sixth valve 45 and the seventh valve 46, and the operation returns to Step S111. If it is~determined in Step S116 that the sixth valve 45 and the seventh valve 46 are closed, the operation returns to Step S111.
If it is determlned in Step S111 that the discharge :~ temperature Td ls not more than~the~first set temperature Tl, ; the operation proceeds to Step S118 to determine whether the : ~ slxth valve 45 and the:seventh valve are open or closed. If it is determined in Step S118 that the sixth valve 45 and the seventh valve 46~are open, the operation pxoceeds to Step S119 to~ close the sixth valve 45 and the seventh valve 46, and the operation return~ to Step S111. If it is detarmined in Step S118 that the sixth valve 45 and the saventh valve 46 are closed, the operation returns to Step Slll.

Third Embodiment :

. , - . . : ::: , , ., ~ : : :.:: . :~ -2097~

Next, a description will be given of the control of the fourth valve 43, the fifth valve 44, the sixth valve 45, and the seventh valve 46 when the low-level pressure has risen above a second set pressure.
Fig. 9 shows a mechanism for controlling ~he fourth valve 43, the fifth valve 44r the sixth valve 45/ and the seventh valve 46, and ref~rence numeral 52 denotes a third control circuit for controlling the fourth to seventh valves by means of ~he pressure de~ected by a fourth pressure-detecting means lo 53.
Fig. 10 is a flowchart illustra-ting the details of control effected by the third control circuit 5 2 .
In the air conditioner in accordance with this third embodiment, in the case of totally heating operation and mainly 1S heating~operatLon when the~heat-source water temperature is ~high, the low-level pressure becomes~high since ~he evaporation temperature is high. Accordingly, control is effected such that the sixth valve 45 and the seventh valve 46 are closed when the fourth pressure-detecting means 53 has detected that zo the low-level pressure lS more than the second set pressure.
Through the above-described~control, the high-pressure liquid refrigerant condensed by the heat exchanger is bypassed to be set to a lower pressure via the caplllary tube, thereby preventing adverse effect from being exerted on the reliability 2s of the compressor.

~ ~ 9 ~

Next, a description will be given of the details of control effected by the third control circuit 52 in this third embodiment with reference to the flowchar~ shown in Fig. 10.
When the air conditioner performs totally cooling operation and mainly cooling operation, in Step S121, a comparison is made between a low-level pressure Ps detected by the fourth pressure-detecting means 53 and a second set pressure P2.
Here, if a determination i5 made that the low-level pressure Ps is greater than the set pressure P2, the operation proceeds to lo Step S122 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed~
If it is determined in Step S122 that the sixth valve 45 and the seventh valve 46 are closed, the operation proceeds to Step S12~ to open the sixth valve 45 and the seventh valve 46.
.15If it i5 determined in Step 5122 that the s1xth val~e 45 and the seventh valve :46 are open, the opera-tion returns to Step ~: ~ S121.
: If it is determined in Step S121 that the low-level ~ pressure Ps is not more than the second set pressure P2, the operation proceeds to Step S124 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed. If it is ~determined in Step S124 that the sixth valve 45 and the seventh valve 46 are open, the operation proceeds to Step S125 to close the sixth valve 45 and the seventh valve 46.

, . .. ... . - - ~ ....... , - ., .- - . . . . , -:.: ::: i ; . : . . , - .

,: .: ~' .. ' ., ' . :, 2097~65 If it is determined in Step S124 that the sixth valve 45 and the seventh valve 46 are closed, the operation returns to Step S121.
When the air conditioner perorms totally heating operation and mainly cooling operation, in Step S126, a comparison is made between the low-level pressure Ps detected by the fourth pressure-detecting means 53 and the second set pressure P2.
Here, if a determination is made that the low-level pressure Ps is-greater than the set pressure P2, the operatLon proceeds to lo Step S127 to determine whether the fourth valve 43 and the fifth valve 44 are open or closed.
If it is determi~ned in Step S127 that the fourth valve 43 and the fifth valve 44 are closed, the operation proceeds to Step S128 to determine whether the sixth valve 45 and the : seventh valve 46 are~open or closed. If it is determined ln :
Step 5128 that the~slxth valve~45 and the seventh valve 46 are closed, the operation proceeds to Step S129 to open the sixth ~ ~ connecting pipe 45~and ~:the seventh valve 46. If it is : determined i.n Step S128 that the sixth valve 45 and the seventh - .

valve 46 are open, the operation returns to Step S126.

If it is determined in Step S127 that the fourth valve 43 :
and the fifth valve ~44 are ~open, the fourth valve 43 and the fifth valve 44 are closed in Step S130, and the operation proceeds to Step S131. In Step S131, a determination is made 25: as to whether the sixth valve 45 and the seventh valve 46 are Y
open or closed. If a determi:nation is made that they are ~ 52 ~

2 ~97~ ~ 3 closed, the operation proceeds to Step S132 to open the sixth valve 45 and the seventh valve 46, and the operation returns to Step Sl26. If it is determined in Step S131 that the sixth valve 45 and the seventh valve 46 are open, the operation returns to Step S126.
If it is determined in Step S126 that the low~level pressure Ps is not more than the second set pxessure P2, the operation proceeds to Step S133 to determine whether the sixth valve 45 and the seventh valve 46 are open or c1osed~ If it is lo determined in Step S133 that the sixth valve 45 and the seventh valve 46 are open, the operation proceeds to Step S134 to close the sixth valve 45 and the seventh valve 46, and the operation returns to Step S126. If it is determined in Step S133 that the sixth valve 45 and the seventh valve are closed/ the operation returns to Step S126.

Fourth Embodiment Next, a description will be given of the control of the fourth valve 43, the fifth valve 44, the sixth valve 45, and the seventh valve 46 when the evaporation temperature has risen above a second set temperature.
Fig. 11 shows a mechanism for controlling the fourth valve 43, the fifth valve 44, the sixth valve 45, and the seventh valve 46, and reference numeral 54 denotes a fourth control circuit for controlling the fourth ~o seventh valves by means of the temperature detected by a second temperature-detectlng :~ . ".
,: .- . :, 209~

means 55. The second temperature-detecting means 55 detects the evaporation temperature at a evaporation-temperature detecting circuit 56 in which the accumulator 20 and the heat source unit-side heat exchanger 19 are connected by means of a capillary tube.
Fig. 12 is a flowchart illustrating the details of control effected by the fourth control circuit 54.
In the air conditioner in accordance with this fourth embodiment as well, the evaporation temperature becomes high in lo the case of totally~ heatln~g operation and mainly heating operation when the hea-t~source water temperature is high.
Accordinglyj control is effec~ed such that the slxth valve 45 and the seventh valve 46 are opened when the second temperature-detecting means 55 has detected that the evaporatlon temperature ~is more than~ the second set temperature. Through the ab~ove-described control,~ the high-pressure liquid;refrigerant condensed;by the heat exchanger is ~bypassed to be set to a lower pressure via the capillary tube, ~ so that the evaporation temperature becomes low, thereby making it possible to secure a cooling capability in the mainly heatlng operation. ~ ~
Finally, a descrl;ption w~ill be given of the details of control effected~ by the fourth control circuit 54 in this fourth embodiment with refer~ence to the flowchart shown in Fig.
2s ~ 12.
::

I . ' ;` .

2~7~ 6~

When the air condltioner performs totally cooling operation and mainly cooling operation, in Step S136, a comparison is made between a evaporation temperature ET detected by the second temperature-detecting means 55 and a second set s temperature T2. Here, if a determination is made that the evaporation temperature ET is greater than the set pressure T2, the operation proceeds to Step S137 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed.
If i-t is determined in S~ep S137 that the sixth valve 45 lo and the seventh valve are closed, the operation proceeds to Step S138 to open the:sixth valve 45 and the seventh valve 46.
If it is determined in Step S137 that the sixth valve 45 and the seventh valve 46 are open, the operation returns to Step S136.
If lt is determined in Step S136 that the evaporation temperature ET is not more than the second set temperature T2, the operation proceeds to Step S139 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed. If it is determined in Step S139 that the sixth valve 45 and the seventh valve 46 are open, the opera-tion proceeds to Step S135 to close the sixth valve 45 and the seventh valve 46.
If it is determined in Step S139 that the sixth valve 45 and the seventh valve 46 are closed, the operation returns to Step S136.
When the air conditioner performs totally heating operation and mainly cooling operation, in Step 5141, a comparison is -. . :.: ~. ~ .: - . - .

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2~7~

made between the evaporation temperature ET detected by the second temperature-detecting means 55 and the second set temperature T2. Here, if a determination is made that the evaporation temperature ET is greater than the set pxessure T2, the operation proceeds to Step S142 to dekermine whether the fourth valve 43 and the fifth valve 44 are open or closed.
If it is determined in Step S142 thak the fou~th valve 43 and the fifth valve 44 are closed, the operation proceeds to Step 5143 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed. If it is determined in Step S143 that the sixth valve 45 and the seventh valve 46 are closed, the operation proceeds to Step S144 to open the sixth 45 and the seventh valve 46. If it is determlned in Step S143 that the sixth valve 45 and the seventh valve 46 are open, khe operation returns ko Step S146.
If it is determlned ln Step~S142 that the fourth valve 43 and the fifth valve 44 are open,; khe fourth valve 43 and the fifth valve 44 are closed in Step S145, and the operatlon , proceeds to Step S146.~ In~Step S14:6, a determination is made as to whether the sixth valve 45 and the seventh valve 46 are open or closed. If a determination is made that they are closed, the operation proceeds~to Step S147 to open the sixth valve 45 and the seventh valve ~6, and the operation returns to Step S141. If it is determined in Step S146 that khe sixth valve 4S and the seventh valve 46 are open, the operation returns to Step S141.
, - 56 -~

- - . .. , ;:, ., , .. . . ~

.' ':
J

~7~

If it is determined in Step S141 that the evaporation temperature ET is not more than the second set temperature T2, the operation proceeds to Step S148 to determine whether the sixth valve 45 and the seventh valve 46 are open or closed. If it is determined in Step S148 that the sixth valve 45 and the seventh valve 46 are open, the operation proceeds to Step S149 to close the sixth valve 45 and the seventh valve 46, and the operation returns to Step S141. If it is determined in Step S148 that -the slxth valve 45 and the seventh valve 46 are closed, the operation returns to Step S141.
As described above, in accordance with -the present invention, it is possible to effect control in such a manner as to suppress an excessive rise in the high-level pressure by :
means of the pressure-detecting means for detecting the 5~ pressure within the discharge-side plpe of the compressor and ~by means~of the~;control clrcuit for controlli.ng the-valves; it is possible to effect control in such a manner as to suppress an excesslve rise in the discharge temperature by means of the temperature-detecting means for detecting the disaharge-side temperature of the compressor and by means of the control circuit for controlli~ng the valves; it is possible~ to effect control in such~a manner~as to suppress an excessive rise in the low-level pressure by means of the pressure-detecting means , for detecting the pressure within the inlet-slde pipe of the 2s accumulator and by means of the control circuit for controlling the valves; and it is possible to effect contxol in such a :: :

,, ; ~

'. : :'' '' ,,: ` '~ .' ' -2~97~6~

manner as to suppress an excessive rise of the evaporation ~:
temperature by means of the temperature-detecting means for detecting the evaporation temperature of the evaporation-temperature detecting circuit which connects the liquid side of s the heat source unit-side heat exchanger and -the inlet of the accumulator and by means of the control circuit. Accordingly, an advantage is offered in that, in an air conditioner in which cooling and heating are effected selectively by a plurality of room units and coollng is~effected by one room unit and heating lo by another, it is possible to perform operation while ensuring a suitable evaporatlon temperature in mainly heating operation, without stopping due to an abnormiality in the high-level pressure and an abnormality In the discharge temperature and without impairing the reliability of the compressor.
: ' ~.

:

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Claims

WHAT IS CLAIMED IS:

1. An air conditioner comprising:
a heat source unit (1) including:
a compressor (17), a four-way changeover valve (18), a plurality of heat exchanger (19) connected in parallel with each other and each having a fourth valve (43) and a fifth valve (44) at inlet and outlet ports thereof, and an accumulator (20);
a plurality of room units (2, 3, 4), each unit including:
a room unit-side heat exchanger (21), and a first flow-rate controller (36);
said heat source unit (1) and said room units (2, 3, 4) being connected to each other via a first connecting pipe (22) and a second connecting pipe (27); and a relay unit (5) including:
a gas-liquid separator (9) disposed in a from unit-side pipe end of said second connecting pipe (27);
first branching section (6) having a first valve (33) and second valve (34) for allowing one end of said room unit-side heat exchanger (21) to communicate selectively with said first connecting pipe (22) or a gas-side output port of said gas-liquid separator (9);
second branching section (8) in which other end of said room unit-side heat exchanger (21) is connected to said first flow-rate controller (36) through said second connecting pipe (27);
second flow-rate controller (7) interposed between said first and second branching sections (6, 8);
a bypass pipe (37) having one end connected to said second branching section (8) and another end connected to said first connecting pipe (22) through a third flow-rate controller (15);
fourth flow-rate controller (16) interposed between said second branching section (8) and said first connecting pipe (22); and heat-exchange portion (10, 11, 12, 13) for effecting heat exchange between said bypass pipe (37) and a pipe (29, 30, 31) connecting together said second connecting pipe (27) and said first flow-rate controller (36);
wherein a gas-side of one of said heat exchanger of said heat source unit-side heat exchanger (19) and a discharge side of said compressor (17) are connected to each other via a sixth valve (45), a liquid side of that heat exchanger and an inlet port of said accumulator (20) are connected to each other via a capillary tube (47) and a seventh valve (46), and there are provided pressure-detecting means (48) for detecting the pressure within a discharge-side pipe of said compressor (17) and a control circuit (49) for controlling such that when the pipe pressure is below a predetermined pressure, said sixth valve (45) and said seventh valve (46) are closed, and when the pipe pressure exceeds the predetermined pressure, said sixth valve (45) and said seventh valve (46) are opened.

2. An air conditioner as claimed in claim 1, wherein a gas side of one of said heat exchanger of said heat source unit side heat exchanger (19) and a discharge side of said compressor (17) are connected to each other via a sixth valve (45), a liquid side of that heat exchanger and an inlet port of said accumulator (20) are connected to each other via a capillary tube (47) and a seventh valve (46), and there are provided temperature-detecting means (51) for detecting the temperature of the discharge side of said compressor (17) and a control circuit (50) for controlling such that when the discharge temperature is below a predetermined temperature, said sixth valve (45) and said seventh valve (46) are closed, and when the discharge temperature exceeds the predetermined temperature, said sixth valve (45) and said seventh valve (46) are opened.

3. An air conditioner as claimed in claim 1, wherein a gas side of one of said heat exchanger of said heat source unit-side heat exchanger (19) and a discharge side of said compressor (17) are connected to each other via a sixth valve (45), a liquid side of that heat exchanger (19) and an inlet port of said accumulator (20) are connected to each other via a capillary tube (47) and a seventh valve (46), and there are provided pressure-detecting means (53) for detecting the pressure within an inlet port-side pipe of said accumulator (20) and a control circuit (52) for controlling such that when the pipe pressure is below a predetermined pressure, said sixth valve (45) and said seventh valve (46) are closed, and when the pipe pressure exceeds the predetermined pressure, said sixth valve (45) and said seventh valve (46) are opened.

4. An air conditioner as claimed in claim 1, wherein a gas side of one of said heat exchanger of said heat source unit-side heat exchanger (19) and a discharge side of said compressor (17) are connected to each other via a sixth valve (45), a liquid side of that heat exchanger and an inlet port of said accumulator (20) are connected to each other via a capillary tube (47) and a seventh valve (46), a liquid side of that heat source unit-side heat exchanger (19) and an inlet port of said accumulator (20) are connected to each other by a capillary tube means (56), and there are provided temperature-detecting means (55) for detecting the an evaporation temperature in said capillary tube means (56) and a control circuit (54) for controlling such that when the evaporation temperature is below a predetermined temperature, said sixth valve (45) and said seventh valve (46) are closed, and when the evaporation temperature exceeds the predetermined temperature, said sixth valve (45) and said seventh valve (46) are opened.